Characteristics of oscillations in magnetic knots of solar faculae

Abstract

The characteristics of oscillations of the intensity, magnetic field, andDoppler velocity in facular magnetic knots are compared with those at the facula periphery, where the magnetic field has a moderate intensity. The analysis is based on images in the FeI 6173 A, 1700 A, and He II 304 A lines obtained with the Solar Dynamics Observatory, which are formed in the lower photosphere, upper photosphere, and transition zone, respectively. The spectra of the oscillations of the longitudinal magnetic field in magnetic knots show peaks at a frequency of about 5 mHz, which are not observed at the faculae peripheries. The spectra of the photospheric oscillations of the intensity and Doppler velocity in magnetic knots and in areas of moderate magnetic field are similar, but the oscillation power is a factor of two to four lower in the knots. The maximum spectral peaks in the HeII 304 A line are mainly distributed in the range 3–6 mHz above magnetic knots and in the range 1.5–3 mHz above periphery regions. It is proposed that this distribution of the oscillations is due to the magnetic-field topologies in faculae: the m